The invention relates to the use of suction cups as a means of holding and manipulating objects. Specifically, the invention is related to a method and apparatus for the use of suction cups on materials with a sensitive surface, such as printing plates.
The use of suction cups as a means of holding and manipulating objects is well known. The basic operation of the suction cup is depicted in FIGS. 1-a and 1-b, which depict a cross section of a suction cup 10. The suction cup 10 is used to hold and manipulate an object 15. FIG. 1-a depicts the parts of the suction cup 10, which typically comprise a flexible contact flange 11 (made out of a soft material such as rubber, which is impermeable to air) and a more rigid structural member 12. The suction cup 10 may generally be of any shape. Typical suction cups are round. The suction cup 10 also normally includes a vacuum hose 13, which is in fluid communication with a pump (not shown).
FIG. 1-a shows the suction cup 10 as it is brought into contact with the object 15 to be manipulated. At this stage, the pump is not activated (i.e. there is no vacuum in the vacuum line 13); consequently, the suction cup 10 is in an inactive mode. FIG. 1-b shows the suction cup 10 when the vacuum pump is activated. When the air is pumped out of the cup""s interior region 14, the reduced pressure inside the interior region 14 draws the suction cup 10 closer to the object 15, causing the object 15 to be held in position at the bottom of the suction cup 10.
A drawback of using suction cups occurs when the object to be manipulated is sensitive to scratching. Referring to FIG. 1-b, when the pressure is reduced in the interior region 14 and the suction cup 10 is drawn closer to the object 15, the flexible contact flanges 11 spread in a radial direction and translate across the surface of the object 15. This translation of the flexible contact flange 11 can scratch, mar or otherwise damage the surface of the object 15.
Despite the scraping action of the flexible contact flanges 11, they are a useful element of the suction cup 10. The flexible contact flanges 11 in combination with the negative pressure created in the cavity 14 by the vacuum hose 13 permit the suction cup 10 to be used on objects 15, which may have uneven surfaces. That is, the flexible contact flanges 11 can bend by variable amounts to accommodate imperfections and deviations in the surface of the object 15.
For some applications of suction cups, this scraping action is not a problem. Such applications include those where the object 15 is a hard object (i.e. relative to the flexible material used in the contact flanges 11) or where the subsequent use of the object 15 is not significantly affected by minor scratching of the object""s surface. However, other applications where this scraping action could be a problem include those where the object is highly sensitive or where the subsequent use of the object requires perfectly homogeneous surfaces (i.e. where a relatively small scratch could corrupt the entire process for which the object is to be used).
It is an object of the present invention to provide an apparatus for a suction cup system, which facilitates the holding and manipulation of a sensitive object without scratching, marring or damaging the surface of the object.
It is a further object of the invention to provide a method of holding and manipulating sensitive objects using suction cups, but without scratching, marring or damaging the surface of the object.
It is a further object of this invention to provide a method and apparatus for the holding anf manipulation of printing plates, which are coated with a layer of sensitive imaging materials. In particular, the method and apparatus should facilitate the holding and manipulation of the printing plate without scratching, marring or damaging the sensitive imaging surface or the plate itself.
In accordance with the present invention, an apparatus designed to hold an object is disclosed. The apparatus comprises a suction cup, with several parts, including: a vacuum hose, an interior region and a flexible contact flange. The vacuum hose is operative to reduce pressure and create a suction force in the interior region of the suction cup. The apparatus also comprises a frame located in the vicinity of the suction cup and a flexible sheet. The flexible sheet is attached to the frame between the suction cup and the object and has at least one aperture, which is aligned with the interior region of the suction cup.
The flexible sheet provides a conformal barrier, which prevents direct physical contact between the flexible contact flange and the object, but which permits suction force to act on the object via the aperture, thereby allowing the object to be held, without scratching, marring or damaging its surface.
Preferably, the apparatus may also include a movement system, which manipulates the object, once held, by manipulating either the suction cup or the frame.
Advantageously, the flexible sheet may have an interior surface, which is in physical contact with the flexible contact flange, such that the flexible sheet sustains any relative motion of the flexible contact flange against its interior surface, without transmitting the relative motion to the object. Additionally, the flexible sheet may sustain any contact with the object against its exterior surface. Preferably, the flexible sheet may be made out of polyester.
Advantageously, the frame may be physically attached to the suction cup.
In a particular embodiment of the invention, the object may be a printing plate, having sensitive imaging materials on one side thereof.
In another aspect of the invention, the apparatus comprises a plurality of suction cups, each suction cup having its own frame and flexible sheet as described above. In this manner, a heavier object may be held and may be manipulated, because of the increased suction force of the plurality of suction cups.
In another aspect of this invention, the apparatus comprises a plurality of suction cups, but there is only one frame and one flexible sheet for the entire plurality of suction cups. Once again, this aspect of the invention facilitates the holding and manipulation of a heavier object, because of the increased suction force of the plurality of suction cups.
Another aspect of this invention involves a method of using a suction cup to hold an object. The method comprises the steps of:
(a) moving the suction cup into the vicinity of the object, such that a flexible contact flange of the suction cup is in close proximity to, but not in physical contact with, the object;
(b) introducing a perforated flexible sheet between the object and the flexible contact flange; and
(c) reducing pressure in the interior region of the suction cup, so as to create a suction force on the object via the perforations in the flexible sheet.
The method requires that the perforations in the flexible sheet be located such that there is at least one aperture aligned with the interior region of the suction cup. When the suction force is applied, it causes the object to move toward, and to be held in contact with, the exterior surface of the flexible sheet. In addition, the suction force causes the flexible contact flange to compress in a manner whereby the flexible contact flange translates along the interior surface of the flexible sheet without physically contacting, scratching, marring or damaging the object.
Advantageously, the method of holding the object may also comprise an additional step of manipulating the object by manipulating the suction cup. The method is independent of what order the introducing step (b) and the moving step (a) are completed.
Preferably, the method may be accomplished using a relatively rigid frame, which supports the flexible sheet. If there is a frame, then it may be advantageous to have the frame attached to the suction cup, because the object may then be manipulated by manipulating the frame.
The flexible sheet may be made of polyester and the object may a printing plate, having sensitive imaging materials on one side thereof.
Another aspect of the invention involves a method of using a plurality of suction cups to hold an object, where each suction cup has its own frame and flexible sheet as described above. In this manner, a heavier object may be held and may be manipulated, because of the increased suction force of the plurality of suction cups.
Another aspect of the invention involves a method of using a plurality of suction cups to hold an object, but where there is only one frame and one flexible sheet for the entire plurality of suction cups. Once again, this aspect of the invention facilitates the holding and manipulation of a heavier object, because of the increased suction force of the plurality of suction cups.